U.S. patent application number 10/463645 was filed with the patent office on 2003-12-25 for mobile station controlling antenna directionality.
Invention is credited to Yamazaki, Toru.
Application Number | 20030236096 10/463645 |
Document ID | / |
Family ID | 29728333 |
Filed Date | 2003-12-25 |
United States Patent
Application |
20030236096 |
Kind Code |
A1 |
Yamazaki, Toru |
December 25, 2003 |
Mobile station controlling antenna directionality
Abstract
A mobile communication terminal mounted in a vehicle sends a
state parameter to a CDMA network through an antenna. The state
parameter includes own position information obtained from an
autonomous positioning device through a communications bus and
detection signals obtained from a vehicle speed sensor and a
gyroscope. The own position information is computed by the
autonomous positioning device based on GPS signals. In the CDMA
network, an azimuth angle from a vehicle-traveling direction to a
base station with which the terminal communicates is computed based
on the state parameter. The azimuth angle is sent as an antenna
control parameter to the terminal. In the terminal, an antenna
control circuit controls directionality of a phased array antenna
based on the antenna control parameter.
Inventors: |
Yamazaki, Toru; (Chita-city,
JP) |
Correspondence
Address: |
HARNESS, DICKEY & PIERCE, P.L.C.
P.O. BOX 828
BLOOMFIELD HILLS
MI
48303
US
|
Family ID: |
29728333 |
Appl. No.: |
10/463645 |
Filed: |
June 17, 2003 |
Current U.S.
Class: |
455/456.6 ;
455/456.1; 455/556.1 |
Current CPC
Class: |
H01Q 21/205 20130101;
H01Q 25/002 20130101; H01Q 21/28 20130101; H04W 16/28 20130101;
H01Q 1/3275 20130101 |
Class at
Publication: |
455/456.6 ;
455/456.1; 455/556.1 |
International
Class: |
H04Q 007/20 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 24, 2002 |
JP |
2002-182871 |
Claims
What is claimed is:
1. A mobile station that travels to a traveling direction at a
traveling speed and communicates from an own position through an
antenna with a plurality of base stations forming a communications
network, comprising: transmitting means for transmitting, to any
one of the base stations, a state parameter that includes the
traveling direction and position-specifying information that
specifies the own position; receiving means for receiving, from any
one of the base stations, an antenna control parameter for
controlling antenna directionality of the antenna, wherein the
antenna control parameter is computed, based on the state
parameter, in the communications network; and antenna controlling
means for controlling, based on the antenna control parameter, the
antenna directionality for aiming at a given base station of the
base stations so as to increase signal strength of a reception
signal from the given base station.
2. A mobile station according to claim 1, wherein the antenna
controlling means controls, according to a direction to any one of
the base stations from the own position, at least one of four
directions, wherein a first direction is a direction on a
horizontal plane of a beam of the antenna, a second direction is a
direction on a vertical plane of the beam, a third direction is a
direction of half beamwidth of the beam, and a fourth direction is
a direction of a null point of the beam.
3. A mobile station according to claim 1, wherein the state
parameter includes, as the position-specifying information, at
least one of own-position information regarding the own position
and base-station information regarding a surrounding base station
of the base stations.
4. A mobile station according to claim 3, further comprising: an
autonomous positioning device, wherein, when the own-position
information is included in the state parameter, the own-position
information includes information that is computed by the autonomous
positioning device.
5. A mobile station according to claim 4, wherein the autonomous
positioning device computes the own position based on GPS signals
from GPS satellites.
6. A mobile station according to claim 4, wherein the autonomous
positioning device predicts a traveling direction and amends, based
on the predicted traveling direction, the antenna control parameter
that is received by the receiving means.
7. A mobile station according to claim 3, wherein, when the
base-station information is included in the state parameter, the
antenna control parameter is determined, in the communications
network, according to a position computed based on the base-station
information included in the state parameter.
8. A mobile station according to claim 1, wherein the antenna
control parameter corresponds to an azimuth angle of the given base
station relative to the traveling direction.
9. A mobile station according to claim 1, wherein the receiving
means measures communications quality of the reception signal of
the given base station, and wherein the antenna controlling means
controls the antenna directionality after amending the antenna
control parameter when the communications quality is determined to
be lower than a predetermined value.
10. A mobile station according to claim 1, wherein the state
parameter further includes the traveling speed, and wherein the
antenna control parameter is amended according to a predicted
traveling direction computed based on the traveling direction and
the traveling speed.
11. A mobile station according to claim 1, wherein the antenna and
the antenna control are included in a phased array antenna.
12. A mobile station according to claim 1, wherein the antenna
includes a fist antenna element and a second antenna element,
wherein the first antenna element is nondirectional for
transmitting the state parameter and receiving the antenna control
parameter, wherein the second antenna element forms a directional
beam for being directed to one of a plurality of azimuth angles,
and wherein the antenna control means controls, based on the
antenna control parameter, the second antenna element for forming
the directional beam for being directed to a required azimuth
angle.
13. A mobile station that travels and communicates from an own
position through an antenna with a plurality of base stations
forming a communications network, comprising: own position
obtaining means for obtaining the own position; base station
position obtaining means for obtaining a position of a given base
station of the base stations, wherein the given base station is
nearby located and communicated with; and antenna controlling means
for controlling, based on the own position and the position of the
given base station, antenna directionality for aiming at the given
base station so as to increase signal strength of a reception
signal from the given base station.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is based on and incorporates herein by
reference Japanese Patent Application No. 2002-182871 filed on Jun.
24, 2002.
FIELD OF THE INVENTION
[0002] The present invention relates to a mobile station which
controls antenna directionality according to a directionality
control parameter computed based on an own position.
BACKGROUND OF THE INVENTION
[0003] Conventionally, there is a wireless access system in which a
wireless link is established by varying a direction and a beam
angle of an antenna of a base station based on position information
of a mobile station estimated by the base station (JP-2000-22618A).
However, directionality of an antenna mounted in the mobile station
is not controlled, so that communications quality in the mobile
station is not sufficiently attained. Hence, the communications
quality needs to be enhanced so as to realize broadband
communications.
SUMMARY OF THE INVENTION
[0004] It is an object of the present invention to provide a mobile
station that controls antenna directionality based on an own
position. This results in enhancing communications quality in the
mobile station.
[0005] To achieve the above object, a mobile station is provided
with the following. The mobile station transmits, to a base
station, a state parameter that includes a traveling direction and
position-specifying information that specifies an own position. It
receives, from the base station, an antenna control parameter for
controlling antenna directionality of an antenna. The antenna
control parameter is computed, based on the state parameter, in the
communications network. The antenna directionality relative to the
base station is controlled based on the antenna control parameter,
so as to increase signal strength of a reception signal from the
base station. This structure enables the antenna directionality to
flexibly correspond to relative position from the mobile station to
the base station. This results in enhancing communications quality
between the mobile station and the base station. Furthermore,
computing the antenna control parameter in the network leads to
lowering of a computation load in the mobile station and rapid
controlling of the antenna directionality.
[0006] It is preferable that a mobile station is provided with the
following. Communications quality of a reception signal from a base
station is measured, and the antenna directionality is amended when
it is determined that the communications quality is determined to
be low. It is further preferable that a mobile station is provided
with the following. The antenna control parameter is amended
according to a predicted traveling direction computed based on a
traveling direction and a traveling speed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] The above and other objects, features and advantages of the
present invention will become more apparent from the following
detailed description made with reference to the accompanying
drawings. In the drawings:
[0008] FIG. 1 is a schematic view showing overall structure
according to embodiments of the present invention;
[0009] FIG. 2 is a block diagram showing structure of a mobile
communication terminal according to a first embodiment;
[0010] FIG. 3 is a flowchart diagram explaining a communications
procedure according to the first embodiment;
[0011] FIG. 4 is a schematic view explaining an antenna control
parameter;
[0012] FIG. 5 is a block diagram showing structure of a mobile
communication terminal according to a second embodiment;
[0013] FIG. 6 is a flowchart diagram explaining a communications
procedure according to the second embodiment;
[0014] FIG. 7 is a block diagram showing structure of a mobile
communication terminal according to a third embodiment;
[0015] FIG. 8 is a flowchart diagram explaining a communications
procedure according to the third embodiment;
[0016] FIGS. 9A and 9B are views showing structure of an antenna of
a mobile communication terminal according to a fourth
embodiment;
[0017] FIG. 10 is a block diagram showing structure of a mobile
communication terminal according to the fourth embodiment; and
[0018] FIG. 11 is a flowchart diagram explaining a communications
procedure according to the fourth embodiment.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0019] (First Embodiment)
[0020] As shown in FIG. 1, a communications system in embodiments
of the present invention includes: a mobile communication terminal
MT (hereinafter referred to "terminal") mounted in a vehicle 1; a
code division multiple access (CDMA) network 4; a plurality of base
stations BS forming the CDMA network 4; the Internet 5 connected
with the CDMA network 4; and an application server (ASV) 6 that is
connected with the Internet 5 and computes an antenna control
parameter (PR). Position determination equipment (PDE) also shown
in FIG. 1 is only used in a third embodiment and explained
later.
[0021] As shown in FIG. 2, the terminal MT includes: an antenna 101
formed of a plurality of antenna elements; an antenna control
circuit 102; a combiner 103; a reception module 104; a transmission
module 105; a data processing circuit 106; a memory storage circuit
107; and a serial input/output interface (I/O IF) circuit 108.
[0022] The antenna 101 is a nondirectional antenna and its elements
(e.g., from four to eight) are disposed, in predetermined spacing,
on a roof of the vehicle 1. Respective phases of output signals of
the antenna elements are controlled by the antenna control circuit
102. Directionality of the antenna 101 as an overall antenna is
thereby controlled for a required direction. This results in
forming a phased array antenna.
[0023] The antenna control circuit 102 has phase shifters (not
shown) whose phasing control amounts are determined by an
instruction value of the data processing circuit 106. The phase
shifters are provided to the respective antenna elements.
[0024] The combiner 103 synthesizes, in receiving, an output signal
from the antenna control circuit 102 to transmit to the reception
module 104. The output signal includes an antenna control parameter
outputted from the respective elements of the antenna 101. The
combiner 103 divides, in transmitting, a transmission signal
correspondingly to the respective elements of the antenna 101 to
transmit to the antenna control circuit 102. The transmission
signal includes a state parameter from the transmission module
105.
[0025] The output signal from the combiner 103 is in the reception
module 104 converted from an analog signal to a digital signal and
into digital information through demodulation.
[0026] The data processing circuit 106 executes data processing for
the digital information to transmit to the transmission module 105,
stores a processing result in the data storage circuit 107, or
obtains information from external devices through the I/O IF
circuit 108.
[0027] The data storage circuit 107 includes ROM where a
communications program is previously stored, and RAM and flash
memory where the processing result and the information from the
external devices are temporarily stored.
[0028] The vehicle 1 includes: a speed sensor 110 that detects a
vehicle speed; a gyroscope 111 that detects an angle of traverse; a
global positioning system (GPS) antenna 120; and an autonomous
positioning device 121 that computes an own current position based
on GPS signals from GPS satellites 3 through the GPS antenna 120.
These detected values and computed result are inputted to the
terminal MT through a communications bus 109.
[0029] Referring to FIG. 3, a communications procedure of a first
embodiment will be explained below. FIG. 3 includes communications
and processing procedures among the terminal MT, the base stations
BS, and the ASV 6. The communications and the processing procedures
are executed by respective computers of the terminal MT, the base
stations BS, and the ASV 6.
[0030] At Step S100, as the terminal MT transmits a link request
and establishes a communications link with a certain base station
(connected base station) BS1 adjoining the vehicle 1, information
regarding the communications link is transmitted to the ASV 6. The
information regarding the communications link includes
identification numbers of the terminal MT and the connected base
station BS1 is transmitted to the ASV 6. Here, typically, there is
interference under radio wave environment relating to the terminal
MT and the antenna 101 of the terminal MT remains nondirectional
before directionality is not controlled.
[0031] At Step S110, the terminal MT transmits the state parameter
(PR) of the terminal MT to the ASV 6 through the connected base
station BS1. The state parameter (PR) of the terminal MT is
obtained by the data processing circuit 106, and includes: a
vehicle current position (x, y) computed by the autonomous
positioning device 121; an averaged vehicle speed and an azimuth
angle of a vehicle-traveling direction; and current time. The
average vehicle speed and the azimuth angle are computed by the
data processing circuit 106 from a detection value of the vehicle
speed sensor 110 and an output signal of the gyroscope 111. The
azimuth angle of the vehicle-traveling direction is computed as an
angle .alpha. to a traveling direction from the north direction in
anticlockwise rotation as shown in FIG. 4.
[0032] At Step S120, the connected base station BS1 transmits an
own position information to the ASV 6.
[0033] At Step S130, the ASV 6 computes, based on the state
parameter transmitted from the terminal MT through the connected
base station BS1, an antenna control parameter as follows: An angle
.alpha.' is computed from the north direction to the connected base
station BS1 based on the current position of the vehicle 1 and the
position of the connected base station BS1.
[0034] An azimuth angle .theta. from the traveling direction of the
vehicle 1 to the connected base station BS1 is computed as
.theta.=.alpha.-.alpha.' based on the angle .alpha. and the angle
.alpha.'. The azimuth angle .theta. is thereby determined as an
antenna control parameter.
[0035] At Step S132, the ASV 6 computes a predictable parameter for
amending the antenna control parameter through predicting an
approaching position as follows: A vehicle position after t minutes
(e.g., 2 to 5 minutes) is predicted from the average speed and the
azimuth angle of the traveling direction; an antenna control
parameter .theta.' at the predicted approaching position after t
minutes is computed similarly with the processing at Step S130. The
predictable parameter .DELTA..theta. after t minutes is computed as
.DELTA..theta.=.theta.-.theta.'.
[0036] At Step S140, the ASV 6 transmits the antenna control
parameter .theta. and the predictable parameter (t, .DELTA..theta.)
to the terminal Mt through the connected base station BS1.
[0037] At Step S150, the terminal MT controls the directionality of
the antenna 101 for directing the antenna beam to the direction of
the connected base station BS1 (at angle .theta. against the
traveling direction) based on the antenna control parameter
.theta..
[0038] This control that is the same as control of directionality
of the phased array antenna is executed by computing based on the
above angle .theta. to control the phase shifters of the antenna
control circuit 102. The antenna control circuit 102 thereafter
controls the directionality of the antenna 101 based on the amended
antenna control parameter that is amended after t minutes by
.DELTA..theta. based on the predictable parameter.
[0039] At Step S160, the terminal MT determines communications
quality of a reception signal received from the connected base
station BS1 through the antenna 101 whose directionality is
controlled. When the quality is determined to be worse than
predetermined quality, the directionality is amended based on the
antenna control parameter as follows.
[0040] The communications quality is evaluated by the data
processing circuit 106 of the terminal MT through measuring signal
to interference ratio (SIR). When the SIR is lower than the
predetermined threshold value, the communications quality is
determined to be lowered. The directionality of the antenna 101 is
thereby amended by the data processing circuit 102 through amending
the antenna control parameter .theta. that is received from the
connected base station BS1. The amending of the directionality of
the antenna 101 is executed by amending the antenna control
parameter .theta. by a predetermined very few degrees of an angle
.DELTA..psi. to clockwise or anticlockwise. This amending of the
directionality of the antenna 101 is repeated until the SIR exceeds
the predetermined threshold value or reaches the maximum value.
[0041] The reception SIR for evaluating the communications quality
of the reception signal can be the same one that is measured for
controlling transmission power in IMT-2000 (international mobile
telecommunications) system. However, reception signal electric
power (an average value) in the terminal MT can be also used for
evaluating the communications quality.
[0042] As the directionality of the antenna is properly attained
for the connected base station BS1, broadband data communications
is started at Step S170.
[0043] According to the first embodiment, the terminal MT
transmits, to the ASV 6, the state parameter including the current
position, vehicle speed, traveling direction, and information
relating to the connected base station BS1. The ASV 6 computes the
azimuth angle to the connected base station BS1 from the terminal
MT, based on the state parameter from the terminal MT, to transmit
as the antenna control parameter. The terminal MT then directs the
directionality of the antenna 101 based on the antenna control
parameter without any computation of the antenna control parameter.
This therefore results in lowering load of computing the antenna
control parameter in the terminal MT and rapid controlling of the
directionality of the antenna 101.
[0044] (Second Embodiment)
[0045] In a second embodiment, a navigation system 122 is connected
to a bus 109 instead of the autonomous positioning device 121 in
the first embodiment, as shown in FIG. 5, and a terminal MT
exchanges position data and a computed result for amending an
antenna control parameter with the navigations system 122.
[0046] The navigation system 122 includes a receiver 123 for
demodulating a reception signal of a GPS antenna 120, a storage
unit 124, and a computing device (NAVI-ECU) 125. The storage unit
124 includes ROM for storing a program and map data for executing a
function of the navigation system, and RAM for storing an antenna
control parameter of the terminal MT along with position data
including position information computed by the NAVI-ECU 125.
[0047] The NAVI-ECU 125 computes a current position of a vehicle 1
based on GPS signals from the receiver 123 and predicts an
approaching position of the vehicle 1 based on the computed current
position, the map data stored in the storage unit 124, and
respective sensor signals from a speed sensor 110 and a gyroscope
111.
[0048] The NAVI-ECU 125 executes the processing of the ASV 6 at
Step S132 in the first embodiment. The NAVI-ECU 125 computes for
amending the antenna control parameter along with receiving, from
the terminal MT, the antenna control parameter and SIR measured
during communications.
[0049] A communications procedure in the second embodiment will be
explained, especially regarding the processing different from that
of the first embodiment, referring to FIG. 6.
[0050] At Step S80, the terminal MT transmits a trigger signal to
the navigation system 122 before starting communications.
[0051] At Step S90, as the navigation system 122 receives the
trigger signal, it computes a current position based on the GPS
signals to transmit to the terminal MT. The computed position data
are stored in the storage unit 124, and a map adjoining the vehicle
1 and a computed position are shown on a liquid crystal display
(LCD) (not shown).
[0052] Processing at Steps S100 to S130 is the same as the
processing in the first embodiment.
[0053] At Step S142, the ASV 6 transmits an antenna control
parameter .theta. to the terminal MT through the connected base
station BS1.
[0054] At Step S144, the terminal MT forwards, as necessary data
for auxiliary control, the received antenna control parameter
.theta. to the navigation system 122.
[0055] At Step S150, the terminal MT controls directionality of an
antenna 101 for directing an antenna beam to a direction of the
connected base station BS1 based on the antenna control parameter
.theta., similarly with the first embodiment.
[0056] At Step S162, the NAVI-ECU 125 determines communications
quality, i.e., reception SIR of the terminal MT. When the reception
SIR is lower than a predetermined threshold value, similarly with
the processing at Step S160 in the first embodiment, amending of
the directionality of the antenna 101 is executed by amending the
antenna control parameter by a predetermined very few degrees of an
angle .DELTA..psi..
[0057] Here, a processing circuit 106 of the terminal MT amends the
antenna control parameter .theta. based on the predicted
approaching position of the vehicle 1 computed by the NAVI-ECU 125,
and an antenna control circuit 102 controls the directionality of
the antenna 101 accordingly.
[0058] The directionality of the antenna 101 of the terminal MT is
directed to the connected base station BS1. This results in
realizing high quality communications.
[0059] At Step S170, broadband data communications is started.
[0060] According to the second embodiment, the terminal MT and the
navigation system exchange data and the navigation system 122
computes amendment of the antenna control parameter that controls
the directionality of the antenna 101 of the terminal MT. This
results in lowering load of computing the antenna control parameter
in the data processing circuit 106 of the terminal MT and enabling
adoption of the terminal whose computing capability is low.
[0061] (Third Embodiment)
[0062] In a third embodiment, position determination equipment
(PDE) 7 provided in the CDMA network 4 computes a current position
of a vehicle 1 necessary for the ASV's computing an antenna control
parameter.
[0063] As shown in FIG. 7, a terminal MT according to the third
embodiment includes a GPS antenna 120 that receives GPS signals
that include satellite numbers and GPS signal transmission time
from the GPS satellites. The GPS signals are inputted directly to a
data processing circuit 106. As explained later, the data
processing circuit 106 transmits, to the CDMA network 4, the
received GPS signals along with state parameter through a
transmission module 105 and an antenna 101.
[0064] The state parameter in the third embodiment includes, in
addition to an average speed, an azimuth angle of a traveling
direction of the vehicle 1, current time, and information regarding
base stations BS surrounding the vehicle 1 (e.g., identification
numbers of the base stations) as information for specifying a
vehicle position. This information regarding the surrounding base
stations is included in pilot signals that the terminal MT receives
from the respective base stations.
[0065] The PDE 7 provided in the CDMA network 4 computes a position
of the vehicle 1 based on position computation request that is
received from the terminal MT through a connected base station BS1
as follows. Here, the PDE 7 and each of the base stations
synchronize with the GPS signals to be operated at the same clock
at which the terminal MT operates.
[0066] The PDE 7 has position information of the respective base
stations along with the identification numbers of the respective
base stations. The PDE 7 receives from the terminal MT the GPS
satellite numbers, position information (e.g., identification
numbers) regarding the connected base station BS1 and the
surrounding base stations BS included in the state parameter from
the terminal MT. The PDE thereby determines the current position of
the vehicle through triangular surveying based on the position
information of the GPS satellites and base stations at the exact
same time.
[0067] A communications procedure in the third embodiment will be
explained referring to FIG. 8, especially regarding different
processing from the first and second embodiments.
[0068] At Step S10, similarly to the processing in the first
embodiment, the terminal MT transmits a link request. At Step S112,
the terminal MT transmits the state parameter. The state parameter
in the third embodiment includes, as information for specifying a
position of the vehicle 1, the surrounding base station information
received by the terminal MT instead of the position information of
the terminal MT included in the first embodiment.
[0069] At Step S114, the PDE 7 computes a current position of the
vehicle 1 to transmit to the ASV 6 at Step S116.
[0070] At Step S120, the connected base station BS1 transmits own
position information to the ASV 6.
[0071] At Steps S130 to S142, the ASV 6 computes an antenna control
parameter .theta. to transmit to the terminal MT, similarly with
the processing in the second embodiment.
[0072] At Step S150 to S170, similarly with the processing in the
first embodiment, the terminal MT controls directionality of an
antenna 101 based on the antenna control parameter .theta. to move
to broadband data communications at Step S170.
[0073] Thus, in the third embodiment, the position of the terminal
MT or the vehicles 1 is computed not by the terminal itself MT, but
by the PDE 7 provided in the CDMA network 4. The directionality of
the antenna 101 is therefore controlled without any autonomous
positioning device in the vehicle 1.
[0074] (Fourth Embodiment)
[0075] In a fourth embodiment, an antenna is not a phased array
antenna but a combined antenna of a first nondirectional antenna
element 1010 and a second directional antenna element 1011. The
first antenna element 1010 is a nondirectional antenna element 1010
while the second antenna element 1011 is formed of six antenna
elements 1011a to 1011f that have beams of predetermined directions
and are disposed in a circumference.
[0076] In FIG. 9A, a perspective view of structure of the antenna
provided in a terminal MT of the fourth embodiment is shown. In
FIG. 9B, radiating beams of the antenna are shown with a traveling
direction of a vehicle 1 being shown in a central top of FIG.
9A.
[0077] The nondirectional antenna element is formed of, e.g.,
monopole antenna element 1010 and provided in a roof (not shown) of
the vehicle 1.
[0078] The directional antenna element is formed of slot antenna
elements 1011a to 1011f using a radial wave guide tube. Two
parallel circular metal plates 1012 form a space, which is then
partitioned into six sectors by three metal plates 1013 that are
radially disposed.
[0079] Each sector has a metal circumferential wall portion 1014,
which has a curved rectangular slot 1015 that has a longer side
(longitudinal side) in a circumferential direction than in a
vertical direction of FIG. 9A.
[0080] Respective feed probes (not shown) of directional antennas
protrude towards a central axis of the sectors from one of the
circular metal plates. The slot antenna element 1011a thereby
radiates a beam within 60 degrees clockwise from the vehicle
traveling direction.
[0081] Similarly, the slot antenna elements 1011b to 1011f radiate
beams within 60 to 120 degrees, 120 to 180 degrees, 180 to 240
degrees, 240 to 300 degrees, and 300 to 360 degrees from the
vehicle traveling direction, respectively.
[0082] Thus, as shown in FIG. 9B, radiating beams from the monopole
antenna element 1010 and the slot antenna elements 1011a to 1011f
are obtained. In particular, when the slot has a longitudinal side
in a horizontal direction, the second directional antenna element
having half beamwidth (angle) can be formed in six directions on a
horizontal plane.
[0083] In FIG. 10, structure of the terminal MT of the fourth
embodiment is shown and the terminal MT has the monopole antenna
element 1010, the slot antenna elements 1011a to 1011f, as
explained above, and an antenna switch unit 1020.
[0084] Output signals from the monopole antenna element 1010 and
slot antenna elements 1011a to 1011f are inputted to the antenna
switch unit 1020.
[0085] The antenna switch unit 1020 is used for switching output
and input terminals, by a control signal from a data processing
circuit 106. Internally, a transmission module 105 or a reception
module 104 is selected. Externally (to the antenna elements), one
of outputs from the monopole antenna element 1010 and slots antenna
elements 1011a to 1011f or synthesized output of adjoining two slot
antenna elements is selected. The antenna switch unit 1020 inputs,
in receiving, a reception signal from one of the nondirectional
antenna element and the directional antenna element to a reception
module 104. It transmits, in transmitting, a transmission signal
from the transmission module 105 through one of the nondirectional
antenna element and the directional antenna element.
[0086] The data processing circuit 106 selects one of the slot
antenna elements according to an antenna control parameter .theta.,
namely an azimuth angle of a connected base station BS1 from the
vehicle traveling direction. For instance, when the antenna control
parameter .theta. is a range from 0 to 60 degrees, the slot antenna
element 1011a is selected. When the antenna control parameter
.theta. is a range from 60 to 120 degrees, the slot antenna element
1011b is selected. And so forth, the respective slot antennas 1011c
to 1011f are selected according to the antenna control parameter
.theta..
[0087] A communications procedure in the fourth embodiment will be
explained below, especially regarding processing different from the
processing in the first embodiment.
[0088] At Step S95, the terminal MT controls the antenna switch
unit 1020 for selecting the nondirectional antenna of the monopole
antenna 1010 and the transmission module 105, so as to communicate
with a base station BS.
[0089] At Steps S100 to S140, processing is the same as the
processing in the first embodiment.
[0090] At Step S155, according to the antenna control parameter
.theta., a required antenna among the slot antenna elements 1011a
to 1011f is selected.
[0091] At Step S165, SIR of a reception signal through the selected
slot antenna element is determined. When the SIR is determined to
be lower than a predetermined threshold value, next SIR of a
reception antenna through a slot antenna element that adjoins, in
clockwise or in anticlockwise, the previously selected slot antenna
element is determined.
[0092] Finally, when the maximum SIR is determined, the slot
antenna element that enables the maximum SIR is selected for
establishing broadband data communications.
[0093] In this case, the antenna switch unit 1020 can synthesize
output signals from two adjoining slot antenna elements through
which the SIR can become the maximum.
[0094] As explained above, in the fourth embodiment, a plurality of
antenna elements whose radiating beams are previously set are used.
Even simple structure of selecting one of the slot antenna elements
can thereby control the directionality of the antenna.
[0095] (Other Modifications)
[0096] The phased array antenna that forms a directional beam by
controlling each phase of the plurality of the non-directional
antenna elements is used for an antenna 101 in the first to third
embodiments. However, an adaptive array antenna can be used. The
adaptive array antenna forms a null point of beam for a
predetermined direction by controlling a weighting coefficient for
amplitude and phase applied on an antenna element. In this case,
the ASV 6 can compute the weighting coefficient as an antenna
control parameter.
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